PHA-Exchange> Delayed Onset of Malaria - Implications for Chemoprophylaxis in Travelers

[Aviva]

From: Dr Rana Jawad Asghar <jawad at alumni.washington.edu>
 
Delayed Onset of Malaria - Implications for Chemoprophylaxis in
Travelers
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By E. Schwartz, M. Parise, P. Kozarsky, and M. Cetron
NEJM - Volume 349:1510-1516 October 16, 2003 Number 16
 
 
A good article in NEJM on Malaria.
 
 
 
ABSTRACT
 
Background 
Most antimalarial agents used by travelers act on the parasite's 
blood stage and therefore do not prevent late-onset illness, par-
ticularly that due to species that cause relapsing malaria. We 
examined the magnitude of this problem among Israeli and American 
travelers.
 
Methods 
We examined malaria surveillance data from Israel and the United 
States to determine the traveler's destination, the infecting 
species, the type of chemoprophylaxis used, and the incubation 
period.
 
Results 
In Israel, from 1994 through 1999, there were 300 cases of ma-
laria among returning travelers in which one species of plasmo-
dium could be identified. In 134 of these cases (44.7 percent), 
the illness developed more than two months after the traveler's 
return; nearly all of these cases were due to infection with 
Plasmodium vivax or P. ovale. In 108 of the 134 cases (80.6 per-
cent), the patient had used an antimalarial regimen according to 
national guidelines. In the United States, from 1992 through 
1998, there were 2822 cases of malaria among travelers in which 
the cause could be evaluated. Late illness developed in 987 (35.0 
percent) of these travelers. The infection was due to P. vivax in 
811 travelers, P. ovale in 66, P. falciparum in 59, and P. ma-
lariae in 51; 614 (62.2 percent) of those with late-onset illness 
had appropriately taken an effective antimalarial agent.
 
Conclusions 
In more than one third of malaria-infected travelers, the illness 
developed more than two months after their return. Most of these 
late-onset illnesses are not prevented by the commonly used and 
effective blood schizonticides. Agents that act on the liver 
phase of malaria parasites are needed for more effective preven-
tion of malaria in travelers.